1. Field of the Invention
The present invention relates to a liquid ejecting head. In particular, the present invention relates to an ink jet printing head effecting printing by ejecting ink to a printing medium.
2. Description of the Related Art
Inkjet print heads (hereinafter also referred to as print head) installed in inkjet printing apparatus eject ink droplets from ejection openings by a variety of techniques, and print by causing the ink droplets to adhere to a print medium, such as printer paper. Among these, it is relatively easy to realize a high-density, multi-nozzle configuration for inkjet print heads that use heat as the energy for ejecting ink, thereby enabling high-resolution, high-image-quality, and high-speed printing.
In recent years, in order to make inkjet print heads more compact and dense, print heads are being used wherein semiconductor fabrication technology is used to internally house an electric control circuit in the print head substrate. The electric control circuit is used to drive ink ejection energy-generating elements. In order to supply ink to a plurality of ejection openings, such inkjet print heads are constructed such that the substrate is pierced from the back surface so that each nozzle communicates with a common ink supply port, thereby supplying ink to individual nozzles from the common ink supply port.
In order to manufacture such inkjet print heads capable of high-quality printing, a manufacturing method for creating an inkjet print head has been disclosed, wherein the dimensions between the nozzles and the ejection energy-generating elements for ejecting ink from the nozzles is controlled with high precision (see Japanese Patent Laid-Open No. H06-286149(1994), for example). In addition, when using a silicon substrate for the inkjet print head substrate, the formation of an ink supply port using anisotropic etching technology has also been disclosed (see Japanese Patent Laid-Open No. H09-011479(1997), for example).
Meanwhile, one reliability factor sought for inkjet print heads is the suppression of dust or other foreign matter infiltrating the nozzles. The cause of dust or foreign matter infiltration is thought to be the contamination of the insides of nozzles by dust or foreign matter during the print head manufacturing process, or by dust or foreign matter being sent together with ink and thereby infiltrating the nozzles.
In order to prevent such infiltration of dust or foreign matter into the nozzles, the provision of a filter onto an inkjet print head has been disclosed.
FIG. 6 is a plan view illustrating an inkjet print head substrate of the related art. Two rows of heaters 6 are disposed along the lengthwise direction of the ink supply port 2. Electrical conducting layers 7 are disposed symmetrically with the heater rows with respect to the ink supply port. A plurality of filter pores 8 are formed on the ink supply port 2.
As one method for manufacturing such a print head, technology has been disclosed wherein, on the substrate surface where the heaters are provided, a resistive material layer is provided at the time of etching the ink supply port, and then a plurality of pores in the resistive material layer are provided, thereby forming a filter and an ink supply port at the same time. (see U.S. Pat. No. 6,264,309, for example). In addition, technology has been disclosed wherein, at the time of forming an ink supply port on a silicon substrate, side etching is used to simultaneously form a membrane filter through an etching-resistant mask applied to the surface opposite to the surface where the heaters are provided (see Japanese Patent Laid-Open No. 2000-094700, for example). Furthermore, technology has been disclosed wherein a membrane filter is provided on the ink supply port portion on the same side of the silicon substrate where the heaters are provided (see Japanese Patent Laid-Open No. 2005-178364, for example).
Meanwhile, in recent inkjet printing apparatus, while droplet sizes of ejected ink are being decreased in order to obtain high-quality images, increased printing speed is also sought. Furthermore, as the printing speed increases, the effects of flow resistance caused by the filter pores become an object of concern.
In order to realize increased printing speed, a sufficient ink flow volume to each bubble chamber must be secured by increasing the surface area of the ink supply port. However, the surface area of the substrate also increases as a result of increasing the surface area of the ink supply port, which leads to higher costs.
One means for holding enlargement of the substrate surface area in check while also securing ink flow volume sufficient to realize high-speed printing involves increasing the filter diameter, while lowering the flow resistance of the membrane portion. However, if the filter diameter is increased, then the mechanical strength of the membrane filter itself decreases. For this reason, the filter may tear, and as a result, yield decreases.